Previous research on the presence and activity of hospitals in social media is abundant, but that is not the case of other health-related organizations. In this research we have examined the profiles on Facebook, Twitter, YouTube and Instagram of 240 health-related entities. It has been proven that health insurers are more present in social networks than the rest, followed by manufacturers of healthcare products, technology companies, pharmaceutical laboratories, biomedical products companies and hospitals. Nevertheless, users interact more with hospitals, although they are less frequent and less active on these platforms. These findings confirm that a greater presence and activity in social media does not correlate with a greater interaction by the public. [ABSTRACT FROM AUTHOR]